The focus of this research is the investigation of molecular mechanisms of opioid activity in an extract of Vitex agnus-castus L. (Chasteberry), used to treat premenstrual syndrome. Chasteberry extract has been shown clinically to improve symptoms of PMS, possibly through binding to opioid receptors. Therefore, it seems prudent to investigate Vitex agnus-castus for relief of PMS symptoms through opioid activity. The purpose of this training grant is to educate the applicant in various identification and characterization techniques, which have particular usefulness in the field of botanical supplements. These techniques will be applied to determine the mechanism of opioid activity for Vitex agnus-castus and compare it to related Vitex species that are often found as common adulterants in a preparation of Chasteberry and will include the following: 1) Identification of the compound(s) that bind to opioid receptors through bioassay-guided fractionation using a cell-based opioid assay. 2) Determination if this compound activates or inhibits opioid receptors. 3) Formal documentation of a botanical, chemical, and biological comparison of Vitex agnus castus to three other species of Vitex that are most commonly found as contaminants.